A wide variety of mufflers of different constructions and configurations are used with internal combustion engines for the purpose of decreasing the acoustical energy of the exhaust gases and thereby reducing the noise pollution in the atmosphere. Generally, acoustical energy is reduced by passing the exhaust gases through a series of expansion chambers and restrictions. However, in most instances, size and shape limitations for the muffler are imposed by the engine manufacturer. Thus, the muffler design, in conforming to the engine manufacturer specifications, must provide a balance between the reduction of acoustical energy while minimizing back pressure in the muffler.